title: Effect of temperature gradient on liquid-liquid phase separation in a polyolefin blend.
abstract: We have investigated experimentally the structure formation processes during phase separation via spinodal decomposition above and below the spinodal line in a binary polymer blend system exposed to in-plane stationary thermal gradients using phase contrast optical microscopy and temperature gradient hot stage. Below the spinodal line there is a coupling of concentration fluctuations and thermal gradient imposed by the temperature gradient hot stage. Also under the thermal gradient annealing phase-separated domains grow faster compared with the system under homogeneous temperature annealing on a zero-gradient or a conventional hot stage. We suggest that the in-plane thermal gradient accelerates phase separation through the enhancement in concentration fluctuations in the early and intermediate stages of spinodal decomposition. In a thermal gradient field, the strength of concentration fluctuation close to the critical point (above the spinodal line) is strong enough to induce phase separation even in one-phase regime of the phase diagram. In the presence of a temperature gradient the equilibrium phase diagrams are no longer valid, and the systems with an upper critical solution temperature can be quenched into phase separation by applying the stationary temperature gradient. The in-plane temperature gradient drives enhanced concentration fluctuations in a binary polymer blend system above and below the spinodal line.
authors.affiliation: Center for Soft Condensed Matter Physics and Interdisciplinary Research, Soochow University, Suzhou 215006, China.
authors.forename: Hua
authors.initials: H
authors.lastname: Jiang
authors.forename: Nannan
authors.initials: N
authors.lastname: Dou
authors.forename: Guoqiang
authors.initials: G
authors.lastname: Fan
authors.forename: Zhaohui
authors.initials: Z
authors.lastname: Yang
authors.forename: Xiaohua
authors.initials: X
authors.lastname: Zhang